Industrial demand accounts for about 30% of total final energy demand in Thailand and is a major source of CO2 emission from energy use. This paper analyzes the changes in industrial energy intensities and CO2 intensities from use of energy over a period of 20 years (1981-2000) and identifies the factors affecting the two intensities using log-mean Divisia decomposition technique. The analysis is carried out in four phases, and the results indicate that both energy intensity and CO2 intensity have declined to some extent. The factor analysis indicates that the intensities declined most between 1981 and 1986 due to reduction in energy intensity and structural changes. In the period of economic boom (1986-1996), intensities increased considerably, thereby negating the benefits of the first period. An increase in energy intensity and a switchover to carbon intensive fuel mix were the important factors for the reversal, although structural effect mitigated the overall increase in intensities of this period. During the economic crisis of 1996-1998, intensities declined once again, due mostly to a fall in energy intensity. In the last period, although energy intensity started to increase, intensities fell due to structural and fuel mix effects. The sub-sectoral analysis indicates that food and nonmetallic industries played an important role in deciding the intensities. (C) 2004 Elsevier B.V. All rights reserved.